" OF TBK 



0NIVEBSITY 



THE CHEMISTRY OF 



SOILS AND FERTILIZERS 



INTRODUCTION 



Prior to 1800 but little was known of the sources 

 and importance of plant food. Manures had been 

 used from the earliest times, and their value was rec- 

 ognized, but the fundamental principles underlying 

 their use were not understood. It was believed that 

 thev acted in some mvsterious way. The alchemists 

 had advanced various views regarding theii action ; 

 one was that the so-called "spirits" left the decaying 

 manure and entered the plant, producing more vigor- 

 ous growth. As evidence, the worthless character of 

 leached manure was cited. It was believed that the 

 spirits had left such manure. The terms 'spirits of 

 hartshorn', 'spirits of niter', 'spirits of turpentine', and 

 many others reflect these ideas regarding the compo- 

 sition of matter. 



Before the composition of plant and animal bodies 

 was established, it was believed that one substance, 

 like copper, could be changed to another substance, as 

 gold. Plants were supposed to be water transmuted 



